A cutting insert according to one aspect has a flat plate shape including a first main surface having a polygonal shape, a second main surface located opposite to the first main surface, and an outer peripheral surface located between the first main surface and the second main surface. The cutting insert includes a cutting portion located in regions including at least a corner portion of the first main surface, and a main body portion located in a region other than the corner portion. A thickness of the main body portion is larger than a thickness of the cutting portions, and the main body portion includes a recessed portion or a protruding portion located in the outer peripheral surface thereof.

Embodiments of a cutting insert are provided. The cutting insert includes an upper surface, a lower surface, a plurality of side surfaces extending between the upper surface and the lower surface, an insert hole extending through the upper surface and the lower surface, and a corner portion provided with a cutting edge. At least one of the upper surface and the lower surface has a plurality of recesses extending between the insert hole and the corner portion. The plurality of recesses includes a first recess into which one portion of the mounting portion is inserted when the cutting insert is supported by the mounting portion, and a second recess into which another portion of the mounting portion is inserted when the cutting insert is supported by the mounting portion. The second recess has a side wall spaced apart from another portion of the mounting portion.

A cutting insert 2 includes an upper surface 6, a lower surface 7 on a side opposite to the upper surface 6, and a peripheral side surface 8 connecting the upper surface 6 and the lower surface 7. A cutting edge 61 is formed in at least a part of a first ridgeline 60 where the upper surface 6 and the peripheral side surface 8 intersect. At least one bottomed recess 10 recessed from the lower surface 7 to the upper surface 6 is formed in an outer peripheral portion of the lower surface 7. Each of the recesses 10 is formed in a substantially triangular shape having a first vertex P, a second vertex Q, and a third vertex R. The first vertex P and the second vertex Q are respectively positioned on a second ridgeline 70 where the lower surface 7 and the peripheral side surface 8 intersect. The third vertex R is positioned on the lower surface 7 and separated from the second ridgeline 70.

An indexable cutting insert has a central mounting portion and two cutting portions. The central mounting portion has opposing upper and lower surfaces. The lower surface has two abutment elements associated therewith, each abutment element having two diverging abutment surfaces forming two abutment angles. The two cutting portions extend away from the central mounting portion, have distal cutting edges, and are entirely located in diagonally opposite imaginary quadrants of four quadrants defined by two mutually perpendicular quadrant planes. Two abutment bisector planes bisecting the two abutment angles and one of the quadrant planes are parallel or coincident. In a top view, the two cutting portions extend away from the central mounting portion in opposite directions. Two cutting bisector lines parallel to the two directions and bisecting the two cutting edges are mutually offset. A cutting tool has an insert holder and the cutting insert removably retained therein.

A cutting tool for turning includes a coupling portion, an intermediate portion and a cutting portion. The intermediate portion extends along a longitudinal center axis thereof between the coupling portion and the cutting portion. The cutting portion includes a first and a second nose portion. The first nose portion has a first cutting edge, a second cutting edge, and a convex nose cutting edge connecting the first and second cutting edges. The first and second cutting edges form a nose angle less than 90°. A longitudinal center axis of the coupling portion defines a tool rotational axis. The cutting portion includes a top surface, the top surface facing away from the coupling portion and the first and the second nose portions each form free ends of the cutting tool.

An assembly of a generally rhombus-shaped reversible cutting insert and a support seat. Each end surface of the cutting insert has a corner abutment surface adjacent each nose cutting edge, at least one inner abutment surface on one side of a lateral plane, and at least one inner abutment surface on the opposite side of the lateral plane, and each corner abutment surface is located closer to a median plane than its adjacent nose cutting edge. In each index position of the cutting insert on the support seat, only one corner abutment surface is in operative contact with one of a plurality of protruding supporting members of the support seat, and only the at least one inner abutment surface located on the opposite side of the lateral plane from the operative corner abutment surface is in contact with the at least one remaining supporting member.

A blade positioning structure of a disposable milling cutter includes a cutter body and a disposable blade. The cutter body is peripherally provided with a blade seat. By passing a screw through the disposable blade and the blade seat, the disposable blade is locked to the blade seat. The blade seat has a blade seat surface and a sidewall; the blade seat surface has a groove; the disposable blade has a bottom surface provided with a projection corresponding in shape to the groove; and when the disposable blade is locked to the blade seat, the blade seat surface and the groove of the latter lie respectively and tightly against the bottom surface and the projection of the former.

A cutting insert includes an insert peripheral surface that includes at least one planar major insert side abutment surface and an insert lower surface that includes an anti-slip recess recessed therein. The anti-slip recess includes at least one elongated and straight anti-slip groove. Each major insert side abutment surface is oriented parallel to a groove longitudinal axis of a respective anti-slip groove. An insert holder includes a holder pocket. The holder pocket includes a pocket peripheral surface which includes planar major pocket side abutment surface and a pocket base surface having an elongated and straight anti-slip rib. When the cutting insert is releasably attached to the insert holder, to constitute a fastened position of a cutting tool, the anti-slip rib is located in the anti-slip groove that is oriented parallel to the major insert side abutment surface that abuts the major pocket side abutment surface.

The present invention provides a cutting tool that can firmly hold four types of cutting inserts by one tool main unit. A cutting insert of a cutting tool 1 has an approximately triangular stereoscopic shape including three corner portions. A tool main unit has a fixing portion that can selectively fix a plurality of types of cutting inserts, including: a negative type cutting insert of which angle of the corner portion exceeds 60°, a positive type cutting insert of which angle of the corner portion exceeds 60°; a negative type cutting insert of which angle of the corner portion is less than 60°; and a positive type cutting insert of which angle of the corner portion is less than 60°. The fixing portion has a bottom face that contacts with a bottom face of the cutting insert, and a side wall face that contacts with a side face of the cutting insert. A portion, which contacts with the cutting insert, of the side wall face of the fixing portion differs depending on the type of the cutting insert.

A turning insert includes a top surface, an opposite bottom surface, and a reference plane therebetween. A center axis intersects the top and bottom surfaces and a side surface connects the top and bottom surfaces. A circular cutting edge is adjacent the top surface and the side surface. The top surface includes a set of first protrusions, which are elongated in a direction parallel to the adjacent cutting edge.. A greatest distance from the reference plane to the first protrusions is greater than a distance from the reference plane to the cutting edge. The bottom surface has a set of radial grooves and includes a set of flat surfaces. The flat surfaces extend in a plane parallel to the reference plane, wherein in a top view each first protrusion is symmetrical in relation to a line extending between the center axis and a mid-point of the first protrusion.